Quadrats are two-dimensional sample units of any size or shape. In some cases, a tape may be laid on the ground at each sampling location to define the quadrat, but more often the quadrat is a frame created from narrow steel or plastic piping and carried from one sampling location to the next. Quadrats are used to measure most vegetation attributes in most vegetation types.
Productivity refers to the biomass produced at a site over a given period of time. Most vegetation assessments are actually limited to estimating net above-ground primary productivity, by ignoring contributions from consumers (livestock, wildlife, microbial populations, etc.). It also circumvents complicated measurements to account for plant respiration and below-ground contributions.
The point transect method is a technique based on point sampling to determine cover. To follow this method, point readings are taken at either systematic or random locations along a tape that is extended to create a transect across the site. A variety of devices, including sighting tubes, bayonets, and plumb-bobs have been used to ensure a vertical reading of the point through the tape.